My neighbour has a metal gate hinged on my external wall. When the
gate is opened it "bangs" on to my wall - and reverberates through my
room.

I want to fasten a rubber buffer/stopper to the wall at the point
where the opening gate strikes it. The problem is that the "strike
point" varies as the contact with the wall is made by a sliding latch
on the gate.

I have tried a rubber door stopper and it is perfect (if the latch
hits it) - except that it is too small.

Ideally I want a piece of rubber 1x1x3 inches.

Any ideas where to get same or similar.